Fire Rainbow

Well it’s not exactly a fire, but it’s the closest thing we could find at this time of year. And the "rainbow connection" seems appropriate given the weather we’ve been having.


This photo contributed by Nev Crocombe.



Origins: This is a real photograph of an atmospheric  phenomenon known as a circumhorizon(tal) arc, the example shown above was captured on camera as it hung for about an hour across a several-hundred square mile area of sky above northern Idaho (near the Washington border) on 3 June 2006.  

In general, a circumhorizontal arc (or "fire rainbow") appears when the sun is high in the sky (ie higher than 58 degrees above the horizon), and its light passes through diaphanous, high-altitude cirrus clouds made up of hexagonal plate crystals. Sunlight entering the crystals’ vertical side faces and leaving through their bottom faces is refracted (as through a prism) and separated into an array of visible colors.  When the plate crystals in cirrus clouds are aligned optimally (i.e., with their faces parallel to the ground), the resulting display is a brilliant spectrum of colors reminiscent of a rainbow. 

Source: New Scientist/London Daily Mail


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